Have you been to relationship counseling with gf? If not, I recommend you try to find a good therapist and go with her. Having an outside adult who hopefully can help straighten things out would be good. Even if you don’t stay together it could help you deal with each other in the future.
Her behavior towards your son is childish and immature. At the same time, she doesn’t need you mansplaining what she should do with the baby’s naps when she IS the one home with him all day.
And I do have some sympathy for the mess she found herself in too. She wanted to be that young couple starting out in love, married, experiencing everything together for the first time as a family. What she stepped into instead was a shaky relationship with a guy who has responsibilities to his first family, wasn’t crazy about having another kid, wasn’t sure about the relationship with her. This is not your fault - she just didn’t think this through and the pregnancy took you both by surprise.
